Electrochemical Behavior of Fe-Si Impressed Current Anodes Testing

摘要

High-silicon cast-iron (Fe-Si) anodes are widely used in anode groundbed applications for underground pipelines and offshore construction. Impressed current anodes are crucial element of cathodic protection systems, their quality assessment must be carried out regularly and properly. In this paper, results of Fe-Si anode sample electrochemical testing in 3% NaCl are presented. The purpose of the testing was quality assessment of silicon iron anodes batches from different manufacturers. A potentiodynamic anodic curve for Fe-Si sample in 3% NaCI was obtained and results of laboratory anodic dissolution test for quality assessment are presented. Secondary test parameters - anode closed circuit potential (CCP), open circuit potential (OCP), pH and appearance of anode samples and electrolyte - allowed us to distinguish between high-quality and faulty samples. OCP of proper samples was not less than minus 0,1 V vs. SCE; for defective samples OCP was close to potential of iron, approx. minus 0,5 V vs. SCE. CCP of high-quality anode samples and pH of their electrolyte was stable, whereas CCP and pH of faulty samples electrolyte changed abnormally. Surface of high-quality material was uniform and smooth, whereas the surface of the faulty material was covered with local corrosion caverns about 10 mm in diameter. Final quality assessment of anode material was based on consumption rate, anode appearance and the secondary test parameters which were carried out. Long-term, full-sized Fe-Si anode grounding electrode test have been started for quality assessment.